There were some drops into the creek that could possibly scrape, say, the rear overhang on your Sequoia. But IIRC it's mostly sand, so all you'd really need to worry about is the pinstripes from overgrown foliage. There were rules a couple years ago about how far you could drive up, especially with a group, due to owl nesting or something. Not sure if it's the same. All I know is that there were people picketing Arch Canyon's use by 4x4 vehicles on a Wednesday morning when I ran it with some of the Wasatch boys. Wondered if those people had actual jobs?
Some rangers watched pretty closely too, I believe they caught up to us while we were eating lunch at the end of the trail just to make sure everything was hunky dory.